Clear room in the fridge for this dessert, and make sure the fridge is really cold, as the various layers must chill quickly.
Heat the oven to 190°C/170°C fan/375°F/Gas 5.
Make the sponge. Put the egg yolks into one mixing bowl and the whites into another. Using an electric whisk, whisk the whites with the salt to soft peaks. Then, whisk in half the sugar. Set aside.
Add the remaining sugar and the vanilla to the egg yolks and whisk until very pale, thick and the whisk leaves a ribbon-like trail when lifted. Gently fold the whites into the yolks. Sift in the flour and fold to combine.
Transfer the mixture to the prepared Swiss roll tin and spread to the corners. Bake for about 15 minutes, until golden and springy. Loosen the sponge, then turn out onto a wire rack, brush with liqueur (if using) and leave to cool. If not using immediately, wrap in baking paper and store in an airtight container overnight.
Make the raspberry jelly. Soak the gelatine in a bowl of cold water until softened. Meanwhile, put the sugar and 200g of the raspberries into a pan with 250ml of water and cook gently, stirring frequently, until the sugar has dissolved and the raspberries are pulpy. Remove from the heat.
Squeeze out the gelatine and whisk into the hot raspberry mixture until dissolved. Strain into a jug, pressing down on the fruit to give a smooth liquid (discard the seeds). Pour into the chilled tin, then decorate the jelly with the remaining raspberries. Chill until set.
Meanwhile, make the yuzu custard. Soak the gelatine as before. Heat the cream in a medium pan over a low heat until almost boiling. Remove the pan from the heat. Put the vanilla paste, egg yolks, and sugar into a heatproof bowl and whisk until pale and creamy.
Slowly whisk in the hot cream, until combined, then tip the mixture back into the pan and stir over a low heat until the custard thickens enough to coat the back of the spoon (don’t let the mixture boil). Remove the pan from the heat, squeeze out the gelatine and stir it into the custard until dissolved.
Stir in the yuzu juice, then strain into a jug and leave to cool, stirring frequently. Once the custard is cold (but still fluid) carefully pour it evenly over the jelly layer in the tin and chill to set.
Make the chocolate bavarois. Soak the gelatine in cold water as before. Put the chopped chocolate into a heatproof bowl. Heat the milk in a medium pan over a low heat until almost boiling, then remove from the heat.
Whisk the egg yolks, sugar and vanilla paste until pale and thick, then gradually whisk in the hot milk. When combined, return the mixture to the pan and stir over a low heat until the custard thickens to coat the back of a spoon (don’t let it boil).
Remove the pan from the heat and stir in the squeezed-out gelatine. Strain the custard over the chopped chocolate, leave for 1 minute, then stir until melted and smooth. Leave to cool, stirring frequently.
Whip the cream until floppy, then carefully fold into the cold, fluid custard. Pour half the chocolate mixture into the tin, on top of the custard, and chill to set. Frequently stir the remaining mixture to prevent it setting.
Make the raspberry mousse. Soak the gelatine as before. Push the raspberries through a sieve to purée and discard the seeds. Pour half the purée into a pan, add the sugar and stir over a low heat to dissolve.
Remove the pan from the heat and add the squeezed-out gelatine, dissolve, and stir in the remaining purée. Leave until completely cold, stirring frequently.
Whip the cream to soft peaks, then fold in the cold purée. Pour into the tin to make an even layer. Chill in the freezer for a few minutes to set quickly.
Spoon the remaining bavarois on top of the raspberry mousse and spread evenly. Cut the sponge into a rectangle to fit on top and gently press in place. Tightly wrap the terrine using the overhanging cling film and chill until set.
To finish, unwrap and turn out the terrine. Whip the cream with the icing sugar until pipeable. Transfer it to the large piping bag. Snip the end and pipe small dots of cream over the top of the terrine. Decorate with raspberries and chocolate curls or shavings, if using. Chill until ready to serve.